One form of sealing arrangement for sealing a conduit for carrying a fluid, that is to say a gaseous or liquid agent includes a closable housing which, in an opened and slackened condition, is fitted with an annular sealing member therein around the conduit or pipe which is to be sealed off. The sealing member of elastomer material has an annular bead affording a sealing surface for cooperating with the wall surface of the conduit. By tightening the housing, the annular bead of the sealing member is moved radially towards the outside of the wall of the conduit until the sealing surface of the annular bead presses against the wall of the conduit, with the required contact pressure force or sealing force. If the gaseous or liquid agent contained in the conduit is subjected to different operating pressures, that is to say a reduced pressure or an increased pressure, the contact pressure force with which the annular bead bears against the wall of the conduit must be adapted and adjusted for the respective differences in pressure and thus force, at the sealing surface, as between the space which is under pressure and the surrounding atmosphere. If an excessively low contact pressure force is applied, the seal my lose sealing integrity when the internal pressure is increased, as the annular bead which for example is of a configuration in the form of a circular arc lifts away from the wall of the conduit. It will therefore be necessary as a precaution to apply an increased contact pressure force in order to be sure of affording an adequate sealing effect, even in regard to the maximum differences in pressure and force which are likely to occur in the sealing region.
When using thin-wall pipes or conduits however, in consideration of the limited strength thereof, the contact pressure force to be applied by the seal my not exceed a comparatively low value which is dependent on the strength of the conduits. That limitation on the contact pressure force to be applied is to be taken into consideration in particular when dealing with pipes of plastic material of lower strength than pipes of metal. However, as stated, that contact pressure force which is admissible only to a limited extent can result in an inadequate sealing effect, in particular when the situation involves fluctuating pressures which cause the seal to be `worked`, that is to say the seal performs micro-movements in the elastic range, and when the situation involves a low pressure or a reduced pressure in respect of the agent, when difficulties occur in terms of providing a sealing effect with conventional sealing arrangements.